Shearing: Metal tearing right near squaring arm within weeks after blade sharpened

I just had the blade sharpened on my Cincinnati Mechanical Shear. Older machine, but we have never had a problem with it. Anyway, when I sheared some 11 Ga. stainless on it there was a slight tearing / pulling on about .25'' of the cut edge, rather than a clean cut. It is happening a few inches in from the squaring arm, leaving a pronounced kerf on the material (and throwing off my overall dimensions because of the resulting different dimensions). I thought maybe it was the gapping, but I tried increasing it and decreasing it and it didn't improve. Its almost as if the blade is dull at that spot now. When I do cuts in the middle of the shear, they come out fine.

Does anyone have any thoughts on what might be the cause? This is the first time I've had the blade sharpened under my ownership. Is it possible that the blade has been sharpened too many times, taking off the hardened surface and making it struggle with stainless steel?

More than likely it is not set correctly. slowly lower the top blade and check the clearance or lack of between the blades. If they are hitting the edge is probably toast. To much clearance tends to fold and tear your work. I have seen blades sharpened so many times they needed to be shimmed up to get the lower cutting edge at the correct height.

I used to be in charge of changing shear knives on 4 different mechanical shears, quarter inch capacity machines- 3 Cincinnatis and 1 Wysong.

Is the top of the bottom knife flush with the top of the shear table? Our blades had been ground so much over the years we had to shim them up to that level. They need to be flush.

Getting that clearance just right is job 1. You are using a feeler gauge while setting that clearance, aren't you?

In reality, it's better to have someone show you than try to explain it to ya over the internet!

It's been 15 years since I did it, so I can't recall what I set the clearances at- it all depended on what gauge material they wanted to shear. Someone on here can surely chime in with the measurements.


Setting the clearance is a 2 man job. It is a pain in the ass to do, no doubt.

Of course you know to, with machine off, step on the treadle to engage the down action, and have one man roll the flywheel to slowly lower the upper knife down about 6 inches each time and measure the clearance at the intersection of the upper and lower knife. We always backed the adjusters off so you didn't take the chance of nicking the edge when starting out, by accident.

How tight you tighten the nuts has a lot to do with the outcome, also. It's a delicate operation to get them to shear thin material, or any material, and not leave a ragged edge or fold it over a bit.

All the things you do make a difference....constant checking with the feeler gauge is a requirement.

I think it might have been the shim on the bottom blade like you said. The machinist that did the repair had one in there, but I am thinking it must have been off a little, because I tweaked it a little bit and tightened and now I am cutting fine again. Thanks for the insight!